Precision prick punch



Aug. 1, 1944.

C. HOUGHTON PRECISION PRICK PUNCH Filed Oct. 8, .1943

1170 INVENTOR.

TTOPIYE) Patented Aug. 1 1944 UNITED STATES PATENT OFFICE Application October 8, 1943, Serial No. 505,568 9 Claims. (01. 33-189) This invention relates to a precision prick punch.

More specifically speaking, the invention relates to a center indicating punch having associated with it means to position the point of the punch proper with great precision in relation to the work upon which the center-indicating indentation is made.

An object of the invention is to provide a center punch having improved punch point positoning means to engage intersecting guide lines scratched in the surface of the piece of work to be operated upon, thereby to enable the workman to position the point of the punch, with precision, vertically above the point to be indented by the punch.

Another object is to provide, for punching center indications, a tool which has a work-containing face a portion of which is cut-away or recessed in such a manner as to enable the workman to tilt the tool so as to unobstruct'his view of the work and thereby enable him to more readily and accurately to place the tool in its proper operative position.

Still another object is to provide the device with a pair of rotatable wheels or disks each of which has a peripheral knife edge adapted to be moved in a practically frictionless manner along a shallow groove or scratch while the punch is being adjusted to the desired position.

Yet still another object is to lessen the friction which has heretofore been encountered in operating center indicating punches. This object is attained, in part, by providing around the punch proper friction reducing clearances, and in part by the novel construction and arrangement of the spring which retracts the punch proper.

Other objects, advantages and features of invention will hereinafter appear.

Referring to the accompanying drawing, which illustrates what is at present deemedto be a preferred embodiment of the invention,

Fig. 1 is a perspective view of the complete device showing the same tilted to a position in which it is placed in one stage of its operation.

Fig. 2 is a side elevation thereof in an upstanding position.

Fig. -3 is a front elevation thereof in an upstanding position;

Fig. 4 is a bottom plan view thereof.

Fig. 5 is a vertical midsection thereof, part of the structure being broken out in order to'contract the length of the view, the plane of section being indicated by the line 5-5 on Fig. 3. This view is on a larger scale than the preceding views.

Fig. 6 is a sectional detail on a still larger scale. the plane of section being indicated by line 66 on Fig. 3.

Referring in detail to the drawing, the punch "character in relation to its diameter, said bore 'having'an upper or body portion l3 within which the shank portion 9 has a working fit, a diametrically reduced intermediate portion it within which the inner part of the shank portion 8 has a working fit, and an inner or lower end portion I5 of a still smaller diameter, within which the punch rod Ill has a working fit.

Where the bore sections l4 and i 5 meet an an nular shoulder l6 results upon which rests the lower end of a spiral compression spring ll which surrounds the rod Ill, the opposite or upper end of said spring abutting against'the lower end of the punch b0dy8 so as normally to retract the point of the punch to the extent shown in Fig. 5. The coils of the spring H are frusto-conioally arranged, the diameter of said spring at its lower end being sufiiciently great to cause that end of the spring to fit snugly within the bore M, Whereas the diameter of the spring at its upper end is sufliciently small to cause its upper coil to fit snugly around the rod Hi. This form of spring is made possible because of the rod i9 being much less in diameter than the part of .the bore section it which it occupies, thereby providing around said rod a sufficiently spacious annular chamber to afford room for the spring when it is constructed in the manner above stated. An advantage is gained by this construction for it keeps nearly the entirelength of the spring out of frictional contact both'with' the bore which it occupies and with the part of the rod l0 which it surrounds.

1 From one side of the lower end of the shank i2 radially projects an arm 28 having a downwardly directed outer end portion or finger 2i furnished with a centering element consisting of a knife edge 22, said knife edge extending in a precisely radial direction in relation tothe axis of the punch rod I 0. Said part 2| has a vertically extending flat surface 23 on one side and the k-nife edge is produced by beveling the side thereof opposite to said vertical surface.

' With'the arm 20 cooperates two twin arms 25 which project radially from opposite sides of the lower end of the shank l2 and both extend in a vertical plane which extends at a right angle to the plane in which the arm 20 extends. Each of said arms 25 has a vertical front face, the front of the tool being regarded as the side thereof from which the arm 20 extends. Each of these and the upper part of the larger face of the disk contacts with the already mentioned vertical face of the arm 25 to which the disk is attached. By this arrangement the disks 2'! are held in place in a very stable, accurate manner.

As shown in Figs. 2 and 5 the tion of the tool shank l2, together with the back sides of the arms 25, is .beveled (or it may be otherwise recessed or cut-away) at 30 from side to side of the tool opposite to the arm 20. This bevel very materially aids the workman in positioning the device properly before striking the punch proper 1 with a hammer to make the center indicating indentation. In positioning the device for this purpose (assuming that two scratch lines intersecting each other at a right third arm from the surface of the work while the knife edges of said wheels remain in contact therewith.

4. The subject matter of claim 1, and each of said wheels being a frusto-conical disk positioned lower end por angle have previously been made upon the work) the workman will first place the knife edges 28 of the disks 21 in one of the scratch lines with the other scratch line in an underlying relation to the arm 20. Then, while still maintaining the disks 2'! in engagement with the scratch line-upon which they have been placed, he will tilt' the tool in such a manner as slightly to clear the outer end portion of the arm 29 from the surface of the Work so that he can see clearly to locate the knife edge 22 of the latter arm precisely over the underlying scratch line, after doing which he will move the shank of the tool to a vertical position, thus bringing all three of the centering elements into engagement with the intersecting scratch lines preparatory to making the center indicating indentation. The workman is aided in positioning the knife edge element ZZby reason of said element being beveled on one side only. In bringing this element down upon the scratch line he will direct his view toward the vertical face of the element 22, which will enable him more clearly to view the underlying scratch line.

What is claimed is:

1. In a device of the kind described,. a tubular shank having a lower end portion provided with two diametrically. opposite radially projecting arms each of which carries a wheel with a peripheral knife edge, means whereby said wheels, are mounted on said arms to rotate in the, vertical plane through which the axis of said tubular shank extends, said shank having a third'arm projecting radially from its lower end portion in a rightangular relation vto the two first recited arms, a centering element carried by said third arm, and a punch proper slidably mounted within said shank and having a point portion located in alinement with the knife edges of the aforementioned wheels.

2. The subject matter of claim 1, and the lower end portion of said tubular shank being cut away at the side thereof opposite to said third arm to provide for a tilting of the applied tool to with- ,draw the centering element carried by said third arm from the surface of the work while the knife edges of said wheels remain in contact therewith.

3. The subject matter of claim 1, and the lower with the larger of its circular faces in contact with a side. portion of the arm whereon it is mounted. I

5. The subject matter of claim 1, and the centering element carried by said third arm consisting of a downwardly directed knife edge which is beveled on one side and has a vertical face at its opposite side to unobstruct the view of the Workman.

6. The subject matter of claim'l, and said tubular shank together with said oppositely projecting arms being beveled from side to side of the tool along the side thereof opposite to said third arm to provide for a tilting of the applied tool to withdraw the centering element carried by said third arm from the surface of the work while the knife edges of said wheels remain in contact therewith.

'7. In a device of the kind described, a tubular shank having a lower end portion provided with two diametrically opposite radially projecting arms each of which carries a Wheel with a peripheral knife edge, means whereby said wheels are mounted on said arms to rotate in the vertical plane through which the axis of said tubular shank extends, and a punchslidably mounted within said shank and having a point portion located in alinement with the knife edges of said wheels.

8. In a device of thekind described, a shank having a lower end portion provided withtwo diametrically opposite radially projecting arms each of which carries a wheel with a peripheral knife edge, means whereby said wheels are mounted on said arms to rotate in the vertical plane through which the axis of said tubular shank extends, said shank having a third arm projecting radially from its lower end portion in a rightangular relation to the two first recited arms, a centering element carried by said third arm, said shank having through it a longitudinal bore, a cylindrical punch slidably fitted within said bore and having at one end an axial rod with apoint projecting from said bore, said rod being diametrically reduced in relation to the adjacent portion of the punch thereby providing around it an annular chamber, the bore also having a diametrically reduced portion within which the terminal portion of said rod slidably fits, and a compression spring in said annular chamber and coiled around said rod normally to maintain the point of the punch in a retracted position, the coils of said spring being frusto conicallyarranged so that only one end portion'of the spring contacts with said rod. i

9. The subject matter of claim 8. and one end portion of said spring fitting snugly 'around said rod and the opposite end {portion of said spring fitting snugly within the part of the b'ore which it occupies. .1 'f CARL HOUGHTON. 

